function A = colrot(A,c,s);

% This function implements the "column rotation"
% algorithm 5.1.6 in Golub and Van Loan, page 203.
% It exploits the fact that there is a 2 x 2 matrix
% which is affected by the Givens rotation, so 
% as to minimize the number of required operations.
% Notation matches Golub and Van Loan


tau1=A(:,1);
tau2=A(:,2);

A(:,1)=c*tau1 - s'*tau2;
A(:,2)=s*tau1 + c'*tau2;   % ' Transposes and Conjugates %



